Transmission circuits



R. V. L. HARTLEY El AL TRANSMISSION CIRCUITS April 6 ,1926. 1,579,931

Filed Oct. 29, 1920 llllllll "1"!" In venfors:

Raw/1 1/4. fldf'f/ey Faber) C Maf/zes y A2734 Patented Apr. 6, 1926.

UNITED STATES PATENT OFFICE.

RAID PH V. L. HARTLEY, OF EAST ORANGE, NEW JERSEY, AND ROBERT C. MAT HES, OF NEW YORK, N. Y., ASSIGNORS TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. 'Y., A CORPORATION OF NEW YORK. I

TRANSMISSION CIRCUITS.

Application filed. October 29, 1920. Serial No. 420,440.

To all whom it my concern:

Be it known that we, RALPH V. L. HART- LnY and ROBERT C. MATHES, citizens of the United States, residing at East Orange, in

the county of Essex and State of New J ersey, and at New York, in the county of :Bronxand State of New York, respectively,

have invented certain new and useful Imrovements in Transmission Circuits, of

1 which the following is a full, clear, concise, and exact description.

This invention relates to repeater circuits for signalin lines and has for an object the provision of a circuit arrangement whereby the input of the repeater may be directly connected to the roper main line section without the necess1ty of employing electfo magnetic transformers.

As is well-known in the art, it is frequently desirable to insert in a signaling line repeaters for the purpose of amplifying or relaying the signaling currents from one line sectionto another, whereby efficient transmission of the signals may be secured over much greater distances than would otherwise be possible. Whenever the repeater set is employed in a physical circuit which is phantomed, it has hitherto been customary to provide a separate repeater for the phantomed circuit, connections "therefor being taken from taps onwindings on repeating coils located on either side of the repeater for the physical circuit. i

Inaccordance with this invention, input connections for the repeater are obtained from impedance such as aresistance connected between the mid-points of two other impedances serially connected in the line.

.The connections between these shunt im- 1 pedances and the in at terminals of the repeater preferably lnclude an auto-transformer for providing the proper impedance relation between'the repeater and the line. Instead of the ordinary repeating coil inserted in the line for obtaining the phantom circuit connections, a single inductance element shunted across the line and tapped at its mid-point is employed. It has also been found desirable at times to employ this direct coupling of the repeater to the line 1n connection with an arrangement in which the output of the repeater is coupled to the outgoing line by a transformer individual to each side of the outgoing line instead of the three limb transformer ordinarily employed, as shown for example in the Grissinger U. S. Patent No. 1,198,212, issued Se tember 12, 1916.

his invention will be better understood by reference to the following detailed de- SCIlPiJlOIh taken .inconnection with the accompanying drawing which represents this invention embodied in a two-way repeater circuit. 0 The two-way repeating system illustrated in the drawing comprises two line sections 4, 5 and 6, 7 between which are included vacuum tube repeaters 8 and 9 for repeatmg signals from line 4, 5 to line 6, 7, and

vacuum tube repeaters 10 and 11 for impressing on line 4, 5 amplified signals of the form received from line 6, 7, Artificial lines 12 and 13 are employed for the well known purpose'of balancing the two line sections 4, 5 and 6, -7 respectively.

Serially included with line section 4, 5 and artificial line 12' are two impedances 14 and 15 which are preferably of the inductive type. Vacuum tube repeater 8 is operatively connected to line section 4, 5 by means of connections 16, 17 taken from intermediate points of an impedance such ,as a resistance 18 which is shunted between the mid-points of inductanccs 14 and 15. In orderto secure the proper impedance relationship between line section 4, 5 and the inputcircuit of repeater 8, it is preferable to employ an auto-transformer 19 therebetween. If desired, the signals amplified or repeated by vacuum tube 8 may be further amplified by a second amplifier 9 before impressing the signals upon the outgoing line section 6, 7. The output circuit of vacuum tube 9 is associated with line section 6, 7 by means of two transformers, the primary windings 21 and 22 of which are inductively coupled to secondary windings 23 and 24, which are connected in shunt respectively to impedances 25, 26. In such an arrangement, signals from line 4 5 Wlll be impressed by means of connections 16, 17 upon vacuum tube amplifiers 8 and 9, and the amplified signals by means of transformers 21, 23 and. 22, 24 will be impressed upon the outgoing line section 6, 7.

In a similar manner, repeating 1n the reverse direction from line 6, 7 to line 4, 5 is obtained by connecting an'impedance such as a resistance 29 between the mid-points of impedances 25 and 26, whereby vacuum tube repeaters 10 and 11 are operatively connected to receive signals from line 6, 7. The amplified signals in the 'output circuit of vacuum tube 11 are impressed on line section 4, 5 by means of transformers 30 and 31, the connections for which correspond to those of transformers 21,23 and 22, 24, previously mentioned.

Since it has been found that vacuum tube repeatersoperate more satisfactorily with the cathodes grounded, special precautions must be taken in order to prevent the ground connection for the cathode from produclng an unbalance of the repeater system, especially in systems such -as above described wherein the input of each repeater 1s cou pled to its proper line section without any intervening two winding transformers. Unbalance eflects however, due to the grounding ofcathode 33 is prevented by having the ground connections symmetrically located with respect to the two sides of line section 4, 5. This is accomplished by connectmg the cathode 33 to the mid-point of that part of inductance 19 bridged across line section 4, 5. Similarly, cathode 34 of repeater 10 is connected to the midpoint of that portlon of inductance 35 bridged across line section v6, 7, whereby the connection to ground is symmetrically located with respect to the two side wires of the line section.

Such a repeater system when balanced properly will operate satisfactorily for repeating signals in either dlrection. In general, however, it may be necessary to insert low pass filters 37 and 38 for preventing the two-way repeater from singing at a high frequency, above the range of frequencies employed in the signaling. These wave filters 37 and 38 may be, for example, of the type shown in the Campbell Patent No. 1,227,113, issued May 22, 1917.

If it is desired to phantom line sections 4, 5 and 6, 7 with other line sections (not shown) in order to provide a third signaling circuit, it will be necessary to provide taps for leading off the phantom circuit currents on either side of the two-way repeater to a phantom circuit two-way repeater, not shown. In accordance with this invention, the phantom taps 39 and 40 are connected to the mid-points of inductances 41 and 42 which are bridged across line sections 4, 5

repeater without the intermediary of any inductive coupling through the two-winding transformer.

In order to prevent the ground connection for cathode 33 from permitting the phantom circuit current being shunted to ground, it will be generally necessary to insert between tap 39 and cathode 33 a retard coil having two windings 44 and 45 wound on a common coil 46 in such a manner as to offer a very high impedance to currents flowing in parallel over conductors 16 and 17 while neutralizing each others impedance for currents flowing serially through conductors 16 and 17. Retard coil 46 will therefore oifer substantially no impedance for the physical circuit currents which are to be amplified by repeater 8, but will substantially block the passage of the phantom circuit currents which it is desirable to lead off over tap 39. In a similarhmanner the other end of the two-way repeater circuit shown in the drawing is provided with a retard coil 48 similar to retard coil 46 for the purpose of offering a high impedance to phantom circuit currents in line 6, 7.

The grounded mid-point of 'that portion of inductance 19 connected in shunt to the main line section 4, 5 also provides a path of low impedance to ground for longitudinal currents of frequencies to which coil 46 offers small impedance, whereby such currents are prevented from impairing the efiiciency of the repeater system. Objectionable longitudinal currents of higher frequencies are of course choked by the coil 46.

Owing to the fact that vacuum tube repeaters are now well known in the art, a detailed description of the circuits for the repeaters has not been given. Reference however, is made to Arnold Patent No. 1,129,942 in which circuit arrangements for tandem repeaters are discussed in detail.

It is to be understood that this invention may be applied to repeater systems widely difi'erent from that described above without departing from the spirit of this invention as defined in the appended claims.

Whenever, in the appended claims, the recital is made that the' input of a repeater is directly coupled to its line section, it is meant that the connection between the repeater and the line section is accomplished without the intermediary of transformers employing a plurality of windings, coupled only inductively.

What is claimed is: 4

, 1. In an electric system, two line sections, a two-way repeater system therebetween comprising a repeater having input terminals and output terminals for, repeating from one of said line sections to the other of said line sections and means associated with said repeater system for leading off the phantom circuit currents from one of said line sections, said input terminals being directly coupled to said first mentioned line section. a

2. Inan electric system, two line sections, a two-way repeater sg'stem therebetween comprising a repeater or repeating in one direction between said line sections, a second repeater for repeating in the opposite direction, said repeaters havinginput and output terminals; and means on each s1de of said repeater system providing a connection, for leading off hantom circuit currents from said line sections, the input terminals of each of said re eaters beingdirectly coupled to one of sai line sections.

3. In an electric system, two line sections, a two-way repeater system therebetween comprising a vacuum tube for repeating in one direction between said line sections, a second vacuum tube for repeating in the opposite direction, each of said vacuum tubes having an anode, a cathode and a control electrode, and means on each side of said re eater system for providing a phantom circult connection around said repeater system, the cathode and control electrodes of each of said vacuum tubes being directly coupled to one of said line sections.

eL-In combination a signaling line, a repeater therefor, and means comprislng a retard coil serially connected in said line for preventing currents flowing in parallel over the side wires of said line from being impressed upon said repeater.

5. In an electric system, two line sections, a repeater system therebetween com rising a vacuum tube having a grounded cat ode and a retard coil having a plurality of windings on a unitary core structure, said windings being so arranged with respect'to each other as to offer high impedance to currents flowing in parallel over the two wires of one of said line sections, while offering a low imedance. to the transmission of currents flowing serially therethrough.

6. In combination, two line sections, a two-way repeating system therefor, comprising a repeater having input and output terminals, an impedance 1n series with each side of'one of said line sections,'a direct coupling connection between mid-points of said impedances and terminals of said' repeater and including an inductance coil of a single winding in shunt to one of said line sections, and a ta to an intermediate point of said winding or withdrawing from said line section the phantom circuit currents.

7. In combination, two line sections, a

two-way repeating system therefor, comprising a repeater having input and output terminals, an impedance in series with each side of one of said line sections, connections from mid-points of said impedance to a plurality of terminals of said repeater, a transformer having a winding in shunt to one of said impedances, a second transformer having a winding Vin shunt to the other of said impedances, a second repeater having input and output terminals, other windings of said.

transformers bein associated with a plurality of terminals 0 said second repeater.

8. In combination, two line sections, a two-way repeating system therefor comprising a repeater having input and output terminals, an impedance in series with each side of one of said line sections, connections from intermediate points of said impedances to .said input terminals, a two-winding transformer having one winding in shunt to one of said impedances, a second two-winding transformer having a winding in shunt to the other of said impedances, and a second repeater having in at and output terminals, theother two win ings of said transformers being connected to the output terminals of said repeater.

9. In combination, two line sections, a repeater system therebetween comprising a repeater having input and output terminals, an impedance in series with one of said line sections, a connection from an intermediate point of said impedance to the input terminals of said repeater, an auto-transformer in said connection, a point of said auto-transformer being connected to ground, an inductance element in shunt to one of said line sections for permitting the withdrawal of phantom circuit currents in said line section, and means for preventing said phantom circuit currents from being shunted to ground through said grounded connection.

10, In an electric system two line sections, a two-way repeater system therebetween comprising a repeater havin input'and outut terminals for repeating rom one of said ine sections to the other of said'line sec tions and means associated with said repeater system for providin a connection around said repeater for p antom circuit currents one set of terminals of said repeater being directly coupled to one of said line sections. s q

11. In combinatiomtwo main line conductors, a two-way repeater I system therebetween, and phantom circuit connections for said conductors, said system comprising a repeater having its input directly coupled to one of said conductors and a substantially symmetrical path to ound for longitudinal currents in said con uctors.

12. In combination, two main line sections, a two-way repeater system therebetween, and

phantom circuit connections for said line In witness whereof, I hereunto subscribe sections, said system comprising a repeater my name this 25th day of October A. D., having its input terminals directly coupled 1920. to one of said line sections and means for RALPH V. L. HARTLEY.

5 preventing longitudinal currents in one of In Witness whereof, I hereunto subscribe said line sections from'being impressed on my name this 5 day of Oct. A. D., 1920.

said repeater. ROBERT C. MATHES. I 

